Higher Nurse-to-Patient Ratio Law Improves Nurse Injury Rates by One-Third

Posted on by Paul Leigh, Ph.D.


California is the only state with a law governing minimum nurse-to-patient staffing ratios. The ratios vary depending on the type of hospital service but are in the range of one nurse for every five patients. (The ratios are available on the California Department of Public Health website.) The law went into effect in 2004.

Lawmakers and stakeholders intended that the law would improve patient safety as more nurses were employed to care for the same number of patients. Whereas many studies show improved patient safety after 2004, no consensus in the scientific literature has emerged.

My colleagues and I sought to answer a different question: could the law improve safety for the nurses themselves? We found that indeed the law did improve safety for nurses and the results were published in the May 2015 issue of the International Archives of Occupational and Environmental Health, “California’s Nurse-to-Patient Ratio Law and Occupational Injury”.

We began with the U.S. Bureau of Labor Statistics’ data set entitled the Survey of Occupational Injuries and Illnesses (SOII). The SOII collects annual data on nonfatal injuries and illnesses derived from 150,000 to over 200,000 private firms, depending on the year. We selected injury and illness data from 1999 to 2009 and combined with data on employment in hospitals in California and the rest of the US from the SOII and the California Employment Development Department. We applied the “difference-in-differences” method whereby the change in injury and illness rates before and after implementation of the law within California were compared to changes in injury rates for the same time period in the 49 other states and DC combined .The “difference-in-differences” method attempts to mimic a randomized trial, based on the assumption that a policy change is enacted independent of the underlying temporal trend in that population’s outcomes. This method helped us account for a nationwide downward trend in workplace injuries and separate the effects of California’s staffing mandates attributable to the new law. We compared differences in years for 2001 to 2003 with 2005 to 2007 for both California and the other 49 states combined.

We found that the law was associated with 55.57 fewer occupational injuries and illnesses per 10,000 registered nurses (RNs) per year, a value 32% lower than the expected rate without the law based on injury and illness rates before the law was enacted. The corresponding estimated reduction in injury and illness rates for licensed practical nurses (LPNs) was 38%.

While the data don’t tell us why the rates went down, the improved staffing ratios could lower rates of injuries and illnesses to nurses in a number of ways. For example, back and shoulder injuries could be prevented, if more nurses were available to help with repositioning patients in bed. Likewise, fewer needle-stick injuries may occur if nurses conducted blood draws and other procedures in a less time-pressured manner. Further research is needed to see if these reductions are maintained over time.

Are you aware of efforts in other states to try to reduce nurse to patient ratios? Please let us know in the comment section below.


 Paul Leigh, Ph.D.

Dr. Leigh is a professor in the Department of Public Health Sciences and the Center for Healthcare Policy and Research at the University of California Davis School of Medicine.


Other study authors, also from UC Davis, were Patrick Romano of the Center for Healthcare Policy and Research and the Department of Internal Medicine, Ana-Maria Iosif of the Department of Public Health Sciences, and Carrie Markis of the Betty Irene Moore School of Nursing.



The research was funded, in part, by the National Institute for Occupational Safety and Health (U54OH007550-11) and the California Department of Public Health (Agreement 09-11543).

Posted on by Paul Leigh, Ph.D.

8 comments on “Higher Nurse-to-Patient Ratio Law Improves Nurse Injury Rates by One-Third”

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    It was an uphill struggle to get the ratio bill passed by voters since corporate money was huge to stop the change. Even after the bill passed, the state administration under Gov Schwartzenegger was pressured by the health industry to water-down or stall implementation of the measure.
    CA nurse staffing ratioes has not driven any health care entity out of business, but it has protected consumers and workers alike from unsafe working conditions. Fewer injuries for nurses means less wasted revenue for time off. Fewer injuries for consumers mean lower liability costs for insurance or court costs. Outcomes for care are better.
    The nursing profession itself drafted this patient protection legislation, did the volunteer work to get the measure on the ballot, and fought the industry pressure to weaken the law. CA has a Nurse Practice Act which places the interest of patients before that of the employers, the individual, the union, or the insurance company. The ratios law is a direct product of that kind of professional commitment.

    Hello, I am Shayari working as a Nurse. My opinion is that nurses works very hard and there is a big risk to their life. Pinch of a small single infected needle could a innocent and helpful life. The government should help nurses in every aspect as possible. Otherwise less people would like to be a nurse.
    Thank you.

    Thank you for this important research. Can you imagine dressing, cleaning, sometimes showering, feeding breakfast and lunch, toileting, moving from bed to chair and back 10 to 12 adults, many of whom can not move on their own in 8 hours( ie each one gets less than an hour for all these activities if you don’t have a minute break. And that leaves no time to sit and hold their hand.

    Nice Article sir, Keep Going on… I am really impressed by read this. Thanks for sharing with us..

    This is quite an important topic and I’m glad you brought this up. I’ve volunteered in several hospitals including UCSF, CPMC, and UCI and saw the tremendous amount of work that they have to do every day. I believe that the correlation of 55.57 fewer occupational injuries and illnesses per 10,000 registered is very much linked to improved staffing ratio. Nurses perform arduous tasks of lifting patients and helping them every day. I firsthandely experienced a nurse supporting her overweight patient onto a wheelchair and it took her almost five minutes to do so. The physical strain on nurses is can be a really big factor that contribute to accidents. Also, from all the hospitals I’ve volunteered about ninety percent of the nurses were petite females that seemed like they would have a hard time supporting someone over 170lbs. Caring for more than five patients at a time would surely increase the likehood for backpain problems and among other things. I have found that there are 12 other states that have enacted this law which is incredibly low. Those states are CA, CT, IL, MN, NV, NJ, NY, OH, OR, RI, TX, VT, and WA. I think another underlying factor is partially due to more volunteer help as well. I’ve been part of discharging patients which is usually a nurse’s job. Several specialized volunteering programs involve working with nurses in one unit. Volunteers can go to patients and ask them if they need anything. This gives nurses more time to do more important tasks and attending to patients that really need them. This along with staffing has made some impact in my opinion. There might be other factors that have been overlooked but all in all, thank you for bringing light into this topic.

    Thanks for sharing it such a great blog. I will definitely be looking forward to work on it. Will keep coming and check your blog for next updates as well.

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